1. FIELD OF THE INVENTION
This invention relates to a high DC voltage generator and particularly to a high DC voltage generator preferably with a nuclear fusion apparatus.
2. DESCRIPTION OF THE PRIOR ART
For example, for a high DC voltage generator to be used as a power supply for a nuclear fusion apparatus, it is necessary to generate a high DC voltage in the order of 100 times the initial service voltage in a short time by reducing the flow of a DC current supplied to a current transformer coil in an extremely short time compared with the time constant of the coil. Then, it is necessary to supply a circuit employing plasma as a conductor which is introduced into an evacuated container of ring-shape (hereinafter referred to as a plasma circuit) with a first-rise current through induction between the current transformer coil and the plasma circuit. For this purpose, there has been suggested an apparatus wherein while a current transformer is supplied with a DC current, the supply of the DC current flowing through the current transformer coil is shut off in a short time by a switching means to allow the DC current of the current transformer coil to flow via a resistor so that the DC current of the current transformer coil is so drastically reduced as to produce a high voltage in the transformer thereby to pass a fast-rise current into the plasma circuit.
Also, it is necessary to apply a magnetic field vertically to the plasma circuit in order to enclose the plasma generated in the plasma circuit stably without causing the plasma to emanate outwardly when the plasma circuit is supplied with a current. The coil for applying the vertical magnetic field must be supplied with a current in synchronism with that of the plasma circuit in order to enclose the plasma in good order. For this purpose, the vertical magnetic field coil must also be supplied with a fast-rise current. It is suggested, therefore, that the vertical magnetic field coil should be supplied with a fast-rise current by applying the high voltage developed across the resistor to the vertical magnetic field coil. After a fast-rise current has been supplied to the vertical magnetic field coil, the vertical magnetic field coil is further supplied with a DC current from another DC current supply device so that a current in synchronism with that of the plasma circuit flows continuously through the vertical magnetic field coil. But, if a current is allowed to flow through the vertical magnetic field coil while maintaining the connection between the current transformer coil and the vertical magnetic field coil, the current transformer coil is supplied with a current reverse to the current which has been flowing so far and the plasma circuit cannot be supplied with current satisfactorily. Therefore, after the vertical magnetic field coil is supplied with a fast-rise current, the vertical magnetic field coil must be controlled independently of the current transformer coil.
The foregoing requirements are applicable to any arrangement wherein a high voltage generated when the supply of a DC current to the first coil is suspended is applied to the second coil, a fast-rise current is supplied to the second coil, then another DC current is supplied to the second coil.